MIMO wireless communication systems comprise multiple-antenna wireless communication devices on both ends of a communication link, e.g., at a base station (BS) and a mobile station (MS). MIMO wireless communication techniques can enhance the radio link reliability and increase the system capacity through diversity gain and multiple signal stream transmission.
Conventional beamforming MIMO systems are unidirectional in that beamforming of multiple streams occurs in one direction from a first device, e.g., a BS, to a second device, e.g., an MS, but not in the other direction from the second device to the first device. It is desirable to exploit the knowledge that can be gained about the channel in both directions between two devices in order to perform bidirectional beamforming MIMO communication between the two devices.